1. Field of the Invention
The present invention relates to a photosensitive recording material, more specifically to a photosensitive material having an improved developing property in a developing process using an aqueous alkaline-developing solution, which is suitable for negative-working photosensitive lithographic plate, color proof, photoresist and the like.
2. Description of the Prior Art
Most photosensitive substances used in negative-working photosensitive composition are diazomium compounds. Among them, diazo resins, such as a formaldehyde condensate of p-diazodiphenylamine are most widely used as photosensitive substances.
A photosensitive composition of a photosensitive layer of a photosensitive lithographic plate using a diazo resin can be generally classified into the following two groups. One of them is a photosensitive composition containing a diazo resin without containing any binder such as disclosed, for example, in U.S. Pat. No. 2,714,066. The other is a one which comprises a diazo resin admixed with a binder component. Recently, most of photosensitive lithographic plates using diazonium compounds comprise diazonium compounds and polymer binders to attain high printing durabilities of the resulting lithographic plates.
The above mentioned photosensitive layer are generally developed in an aqueous-alkaline developing solution which can remove unexposed areas from the photosensitive layer. However, especially in the case of a photosensitive lithographic plate, it has been known that a developing property become degraded as a storage time goes by after the production of the plate, which results in background contamination in printing process. Background contamination in printing would arise in the case where a lithographic plate is used after storage for a certain period even if background contamination does not arise in the case where it is used immediately after the production. The above disadvantages are particularly remarkable when the plates are stored under a hot and humid condition. It has been desired, therefore, to obtain a photosensitive lithographic plate which can be stored for a long time, especially under a hot and humid condition, without yielding background contamination in printing process.
Many proposals have been reported to overcome the disadvantages. Examples of the proposals include a photosensitive lithographic plate having an undercoating layer comprising a polyvinyl-phosphonic acid on the surface of an anodized aluminum plate and a photosensitive layer containing diazonium compound on the undercoating layer (West German Patent No. 1,621,478), a photosensitive lithographic plate having an undercoating layer (e.g., of polyacrylic acid) on an aluminum substrate and a photosensitive layer comprising diazo resin on the undercoating layer (West German Patent No. 1,091,433), a photosensitive lithographic plate having an undercoating layer of polyacrylamide and a photosensitive layer on the undercoating layer (U.S. Pat. No. 3,511,661), the addition of a high molecular organic acid into a photosensitive layer which comprises a diazonium compound and an organic polymer-carrier in order to improve storage-stability and to prevent background contamination (Japanease Patent Published Unexamined Application (hereinafter referred to as J. P. KOKAI) No. 56-107,238). However, all the above proposals remain inefficient in terms of improving the stability of the lithographic plate. Therefore, further improvements have been desired. U.S. Pat. No. 4,408,532 discloses a photosensitive composition comprising a diazo resin having multiple diazonium side chain groups in combination with a sulfonated polymer having multiple sulufonate groups such as a sulfonated polyurethane or a sulfonated polyester. However, the composition fails to give sufficient improvement with regard to reducing background contamintaion in printing, and the use of the composition is quite nallowly restricted because the composition is used as a photosensitive layer so that the properties of the photosensitive lithographic plate is necessarily determined by the properties of the sulfonated polyurethane or sulfonated polyester.